How does a W-2 Nurse Practitioner deduct education and recertification fees?

There is no error to fix.  Since 2018, W-2 employees are not allowed to deduct job expenses, including continuing education classes and professional memberships or licenses.  TurboTax only allows you to complete form 2106, because job expenses are deductible on state returns in AL, AR, CA, HI, MN, NY or PA.  If so, this will come up in the state interview, in TurboTax. 

 Even in the "old days" , job expenses were only a misc. itemized deduction.  You only got to deduct that portion of  your misc. itemized deductions that exceeded 2% of your AGI,  and then only if your total  itemized deductions exceeded the standard deduction (which was doubled under the 2018 tax law. .  (2% rule explained: https://ttlc.intuit.com/questions/2902781-what-is-the-2-rule ).

If she is not self-employed, those expenses are not deductible as job-related expenses.   You can leave Form 2106 included in your return, as her state may allow the deductions, but for tax years 2018-2025, job-related expenses for employees are no longer deductible on most people’s federal return.  

Depending on the courses she is taking, she may qualify for the Lifetime Learning Credit.